1. Field of the Invention
This invention relates to a system for detecting a malfunction which may occur in an internal combustion engine, more specifically to a system for detecting a malfunction which may occur in a part such as the fuel injector in the internal combustion engine.
2. Description of the Prior Art
When a malfunction occurs in a part of an internal combustion engine such as the fuel injector, it is important that it be detected immediately and troubleshooted as soon as possible. Japanese Laid-open Utility Model Application Hei 3(1991)-6,037 describes a malfunction detection system for an internal combustion engine, in which the fuel injection quantity is determined for four individual cylinders by adjusting the basic fuel injection quantity using cylinder-by-cylinder correction factors which are in creased/decreased in response to detected individual cylinders' air/fuel ratios. In the system, the correction factor for a certain cylinder is compared with those for the other three cylinders and if the deviation is significant, it is assumed that the fuel injector for the cylinder concerned has become clogged. More specifically, the correction factors for the other three cylinders are averaged and the average obtained is compared with the factor for the cylinder in question. If the factor is found to exceed the average, the fuel injector for the cylinder is assumed to be clogged.
Thus, in order to detect the fuel injector's malfunction, in the prior art system, it is necessary to calculate the average value of the correction factors. The system is disadvantageously complicated, and the detection accuracy is not always satisfactory, leaving much to be desired.
An object of the invention therefore is to solve the drawbacks of the prior art system and to provide a system for detecting a malfunction occurring in an internal combustion engine in a part such as the fuel injector, which can detect a malfunction immediately but has a less complicated structure and improved detection accuracy.
Moreover, although the prior art system is capable of detecting a malfunction such as the fuel injector's trouble which may occur locally at a certain cylinder, the system is unable to detect a malfunction which may occur in the overall system such as the fuel supply system of the engine common to all the cylinders.
Another object of the invention therefore is to provide a system for detecting a malfunction occurring in an internal combustion engine which is also able to detect a malfunction in the overall engine system common to all the cylinders.